Exploring speech envelope enhancement for auditory intervention in children with dyslexia
It is well established that the dominant core deficit in dyslexia is phonological, but there is growing evidence that subtle speech perception deficits precede the phonological difficulties. Recent theories attribute impaired speech perception in dyslexia to altered processing of dynamic features of the speech envelope, such as slow amplitude fluctuations and transient acoustic cues. Therefore, if speech perception deficits in dyslexia indeed stem from faulty speech envelope tracking, then consequently enhancing the envelope might improve speech perception by persons with dyslexia.
In our previous study we implemented an envelope enhancement strategy (EE) to amplify specific amplitude transition in the envelope, without affecting other parts of the speech signal (Koning and Wouters 2012) in an adult population. We hypothesized that emphasizing these challenging dynamic features might strengthen information processing of syllable onsets and phoneme discrimination and in turn ameliorates speech perception for adults with dyslexia. We found that EE instantaneously improved atypical speech perception in adults with dyslexia.
In the present study, the objective is to generalize these results to a younger population. Therefore, we tested children, age 9 to 12 years, with and without dyslexia using a sentence repetition task in a speech-weighted background noise. We tested speech perception in four different conditions: natural speech, vocoded speech and their enhanced versions. These conditions were used to assess both the nature of the speech perception deficit and the effect of the EE-algorithm on speech perception. Additionally, cognitive test of phonological awareness, language skills, verbal short term memory and working memory were administered to investigate possible confounding effects. The preliminary results of this study will be discussed at the conference.